Carboxylic acids such as acetic acid have been known as industrial chemicals for many years. Acetic acid is used in the manufacture of a variety of intermediary and end-products. Many modern processes for producing such carboxylic acids are based on the carbonylation of alcohols such as methanol. Many acetic acid carbonylation processes have been developed and commercialized using homogeneous catalyst systems involving Group VIII metals such as rhodium, iridium, ruthenium and combinations of metals. Such homogeneous processes create the need to separate the catalyst from the product stream. Recovery of metals for reuse also becomes important because catalyst metals are often expensive. These issues create the need for additional construction and operating costs. Considerable effort has been directed to develop heterogeneous catalysis processes for carbonylation in which the catalyst material remains in a solid phase and thus remains separate from the product stream. One challenge of for such systems is ensuring stability of the catalyst metals and related compounds in the solid phase and resistance to leaching into the product. This is particularly true for liquid phase processes. Accordingly, there is a need for a catalyst which can be used in either a vapor phase or liquid phase carbonylation process for the production of carboxylic acids and their esters and in which the catalyst is maintained in the solid phase.